And that’s not the only thing lurking on your cash. 

$100 bill with Benjamin Franklin wearing a mask.

Call it dirty money. Or even an argument in favor of money laundering?

Jokes aside, a new study released Sunday by the Australian Centre for Disease Preparedness finds that the coronavirus can live on your cash—as well as phone screens and other common surfaces—for up to about 28 days when it’s kept at room temperature (roughly 68 F). The flu, meanwhile, lives about 17 days.

And it’s not just the coronavirus that may be clinging to your money. One 2017 study of $1 bills revealed that more than 100 different kinds of bacteria were living on the money. Another 2002 study revealed that 94% of $1 bills contained “pathogenic or potentially pathogenic organisms,” which suggested “a high rate of bacterial contamination of one-dollar bills.” 

Among the unsavory bacteria that are sometimes found on our currency: antibiotic-resistant MRSA and E.coli. Some research shows that there are more germs on money than on a toilet.

But can all these germs make you sick? Maybe. “The precise role of surface transmission, the degree of surface contact and the amount of virus required for infection is yet to be determined,” Debbie Eagles, the deputy director of the Australian Centre for Disease Preparedness and co-author of the study, said in an emailed statement to Bloomberg on Monday. Other researchers told the BBC that the spread of the coronavirus through surfaces required more study under different conditions. 

So what should you do to keep yourself as germ-free as possible when handling cash? Always wash your hands with soap after handling money, consider keeping hand sanitizer around for when that is not possible, and consider wearing gloves.